The words ferri-, ferry sound the same but have different meanings and spellings. Why do ferri-, ferry sound the same even though they are completely different words?
The answer is simple: ferri-, ferry are homophones of the English language.
Iron, especially ferric iron: ferricyanide.
Nautical To transport (people, vehicles, or goods) by boat across a body of water.
Nautical To cross (a body of water) by a ferry.
To deliver (a vehicle, especially an aircraft) under its own power to its eventual user.
To transport (people or goods) by vehicle, especially by aircraft.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.